This application relates to audible displays and more particularly to the conversion of various salient features of signals in an electrical circuit (digital or analog) into audibly distinct sounds which are transmitted to a user through a speaker or headphones.
Electrical circuits generate signals which include various salient features reflective of many types of significant information therein. It is often necessary to test or sample such signals either to see if the circuit is operating correctly or to gather intelligible information from the various features thereof. One widespread technique for sampling signals from electrical circuits and visually displaying various characteristics thereof is by means of an oscilloscope which produces a visual display of one or more electrical signals. The display on an oscilloscope screen carries various types of differentiable information of the signal being sampled. Such signal characteristics include pulse width, duty cycle, activity level, signal level, pattern repetition comparison, and others. A test operator or user can visually determine whether the various characteristics of the signal are proper, or alternatively gather significant information from the various characteristics of the electrical signals which characteristics may be representative of the proper functioning of equipment, or even the monitoring of physiological aspects of the human body.
While the oscilloscope is undoubtedly a highly important and useful electronic instrument, there are limitations to its usefulness. First of all, of course, the operator or user must be able to see the oscilloscope screen. In addition to the obvious situation that this is impossible for a blind operator, there are many other instances when it is disruptive to the test procedure or other operation being carried on to shift visual attention of the operator from the electrical circuit, equipment, work piece, or portion of the human anatomy being worked upon at the time to the oscilloscope or other visual display to view the sampled signal or features thereof. In such instances, the only known manner to accomplish this is to have a second person reading the results from the visual display. This is obviously not always a satisfactory solution either from the standpoint of efficiency and economy or from the standpoint of satisfactory utilization of operator skills.
Human hearing is a remarkable sense or attribute of the central nervous system, especially in its ability to provide discrimination information. Human beings can recognize a familiar voice over the telephone in a second or less because of sound differences; a mother can distinguish the difference between the "fussing" and "distress" cries of her baby. Automobile operators all have the experience of detecting malfunctions in their vehicles simply because of sound differences. Similarly, doctors and automobile mechanics gain valuable information from the stethoscope.
There have been some rather primitive attempts to utilize sound as an indication of a limited feature of an electrical signal. For example, one type of auditory analysis of electrical signals, represented by U.S. Pat. Nos. 4,160,206; 4,321,530; and 4,350,951, generates an audible test signal responsive to a single electrical aspect to be tested. For example, the tone difference in the audible sound is generated when a measured electrical characteristic, such as voltage, current, or resistance, has exceeded a prescribed range.
In a second type of audible signal generator, evidenced by prior literature, binary information is translated from some type of meter, such as a volt meter, to an audible signal. This is relatively easy by utilizing such features as note pitch to discriminate between the two states of a binary signal. Thus, a high pitch may be indicative of a 1 and a low pitch may be indicative of a 0. The output signal is thus a code of high and low pitches which is indicative of a binary number.
A third type of auditory electrical signal device is what is referred to as a "signature analysis test procedure" where the signal at a prescribed node is compared with a standard or good signal. An audible sound, such as a beep, indicates "pass" or "fail." Also, as taught in U.S. Pat. No. 3,800,082 a type of reading machine has been developed which converts two-dimensional patterns into frequency and amplitude auditory signals for blind persons to enable them to determine various shapes. In this approach, a television camera scans a two-dimension pattern and the vertical position of the scan is represented by the frequency of the tone heard while the horizontal position of the scan is represented by amplitude.
While auditory signal generators, as described hereinabove, have been utilized in the limited senses set forth it is not believed that audible displays have been used to analyze simultaneously or collectively the different salient features of an electrical signal in the manner that an oscilloscope is used to visually analyze such signals.